Method for locating a catheter tip using audio detection

ABSTRACT

A method for locating a catheter tip within a human body is disclosed. An audio sensor is positioned at a site on the human body. An audio signal is detected by the audio sensor, and transmitted to an audio signal processing unit. The audio signal processing unit determines if the audio signal corresponds to a target location of the catheter tip, and transmits a notification signal to a user notification unit. An infusion of fluid or an audio emitting element can be used to generate the audio signal at the catheter tip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application No.61/388,675 filed on Oct. 1, 2010 incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present invention relates generally to a method for locating acatheter tip within a human body. More specifically, the inventionrelates to a method for locating a catheter tip by detecting audiosignals emitted from the catheter tip, processing the detected audiosignals, and verifying that the catheter tip is at the target location.

BACKGROUND OF THE INVENTION

Medical professionals commonly use catheters for gaining pro longedaccess to an area within the body. Once the catheter tip is positionedat the target location, treatments such as antibiotics, chemotherapy,pain medicine, and nutrition can be administered. However, if thecatheter tip is improperly positioned during insertion, or if thecatheter tip migrates out of position after insertion, various risksarise, including a fluid infusion that causes pain or injury to thepatient, complications due to increased thrombosis rates, delays intherapy, catheter malfunction and additional costs.

The general standard for proper catheter insertion depends on the typeof catheter and the type of treatment. For example, peripherallyinserted central catheters (or PICC lines) are commonly inserted into abrachial, cephalic or basilic vein in the arm and advanced through thevenous system towards the superior vena cava. Current medical standardsrecommended that the distal tip of the catheter terminate in the lower ⅓of the superior vena cava, close to the junction of the superior venacava and the right atrium. However, since PICCs are commonly insertedinto a vein in the arm and advanced through the venous system to reachthe superior vena cava, the PICC line tip may be inadvertentlypositioned in a non-target area, such as the internal jugular orsubclavian vein. Further, even if a PICC is properly inserted, thecatheter tip could later shift out of position if for example thepatient coughs violently, moves a lot, or experiences severe vomiting.Therefore, verifying that the catheter tip is in the correct location isessential for safe operation of the catheter.

Catheter tip location techniques have improved the ability of medicalprofessionals to verify the location of the catheter tip. One techniqueuses fluoroscopy to confirm tip location. Fluoroscopy provides theoperator with real-time images of the patient's anatomy using afluoroscope. Another technique uses electromagnetic detection and astylet having an electromagnetic sensor placed inside the lumen of thecatheter tip. Electromagnetic systems use an external device positioneddirectly over the internal target area for generating a magnetic fieldoutside of the body. The electromagnetic sensor on the stylet is theninserted into the body through the catheter lumen and measures when themagnetic flux is at its greatest. A monitor indicates to the user whenthe electromagnetic sensor on the stylet is centered underneath theexternal device. In a variation of this technique, the external devicesenses the electromagnetic field, and an element at the tip of thestylet generates the electromagnetic field. Another technique usesultrasound for guidance and determining catheter tip location.Electrocardiogram technology is also used determine catheter tiplocation by measuring the change of the P wave as the catheterprogresses down the superior vena cava.

However, the systems and techniques described above have numerousdeficiencies. Fluoroscopy requires a facility with fluoroscopy machine,and poses x-ray risks for both the patient and the operator. Further,interpreting the image in fluoroscopy and ultrasound can be difficult,and requires special training. Electromagnetic detection requires astylet having an electromagnetic detecting or emitting component, andmeasurement accuracy can be disrupted by electromagnetic interference.Further, for patients with pacemakers or skin disorders, or for patientsthat are obese, device operability may dramatically decrease or becontraindicated. Electrocardiogram detection requires a normal sinusrhythm, and cannot indicate when the catheter tip is in locationsincluding the jugular vein and the subclavian. Additionally, thetechnology associated with the tip location systems mentioned above canbe cost prohibitive, decreasing the number of facilities properlyequipped to perform catheter insertion and maintenance procedures.

Therefore, a new method of locating a catheter tip within a human bodyis desired in order to overcome or minimize the deficiencies describedabove.

SUMMARY

The present invention is directed to a method of locating a catheter tipwithin a human body using audio detection.

In one embodiment, a method for locating a catheter tip within a humanbody includes positioning an audio sensor at a site on the human bodyand infusing fluid through an opening in the catheter tip. An audiosignal is detected through and transmitted to an audio signal processingunit. The audio signal processing unit determines if the audio signalcorresponds to a target location of the catheter tip, and transmits anotification signal to a user notification unit.

In another embodiment, a method for locating a catheter tip within ahuman body includes inserting a catheter into a hollow anatomicalstructure of the human body. The catheter includes an elongated bodyhaving a proximal end and a distal end terminating in a catheter tip, alumen having an opening disposed at the distal end, and an audioemitting element configured at a distal portion of the elongated body.The catheter is advanced at least partially through the hollowanatomical structure. An audio sensor is positioned at a site on thehuman body. An audio beacon signal is emitted from the audio emittingelement, and an audio signal is detected through the audio sensor andtransmitted to the audio signal processing unit. The audio signalprocessing unit determines if the audio signal corresponds to a targetlocation of the catheter tip, and transmits a notification signal to auser notification unit.

In another embodiment, a method for locating a catheter tip within ahuman body includes inserting a catheter into a hollow anatomicalstructure of the human body. The catheter includes an elongated bodyhaving a proximal end and a distal end terminating in a catheter tip,and a lumen having an opening disposed at the distal end. An audioemitting element is positioned at the catheter tip. The catheter isadvanced at least partially through the hollow anatomical structure. Anaudio sensor is positioned at a site on the human body. An audio beaconsignal is emitted from the audio emitting element and an audio signal isdetected through the audio sensor and transmitted to an audio signalprocessing unit. The audio signal processing unit determines if thefirst audio signal corresponds to a target location of the catheter tip,and transmits a notification signal to a user notification unit.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing purposes and features, as well as other purposes andfeatures, will become apparent with reference to the description andaccompanying figures below, which are included to provide anunderstanding of the invention and constitute a part of thespecification, in which like numerals represent like elements, and inwhich:

FIG. 1 is a view illustrating an application of the method according toan example embodiment of the present invention.

FIG. 2 is a cutaway view of a heart being accessed by a catheterinfusing a fluid bolus.

FIG. 3 is a flow chart of the method according to an example embodimentof the present invention.

FIGS. 4A-4D show various catheter tip positions and a corresponding userconsole display according to an example embodiment. FIG. 4A shows a userconsole display when a catheter tip is positioned in a vein in theshoulder. FIG. 4B shows a user console display when a catheter tip ispositioned in the lower ⅓ of the superior vena cava. FIG. 4C shows auser console display when a catheter tip is positioned in the internaljugular vein. FIG. 4D shows a user console display when a catheter tipis positioned in the subclavian vein.

FIGS. 5A-5C show a piezo film audio sensor. FIG. 5A is a top view of apiezo film audio sensor, including cross-sectional views A-A and B-B.FIG. 5B is a top view of a piezo film audio sensor with leadattachments. FIG. 5C is a top view of an audio sensor within aprotective layer, including cross-sectional views C-C.

FIG. 6 is a block diagram of audio signal processing according to anexample embodiment.

FIG. 7 illustrates an electrocardiogram electrode and an audio sensorcommunicating wirelessly with a user console according to an exampleembodiment.

FIGS. 8A-8D show example embodiments of an audio emitting elementlocated at the catheter tip. FIG 8A is a side view of a catheter with aflexible elongated member having a piezo audio emitting elementconfigured at the distal portion extended through a lumen in thecatheter. FIG. 8B is a side view of the distal portion of the flexibleelongated member having a piezo audio emitting element. FIG. 8C is aside view of a catheter having a piezo film audio emitting elementconfigured at the distal portion. FIG 8D is a side view of a piezo filmelement with communication elements extending proximally.

DETAILED DESCRIPTION OF THE INVENTION

The present invention can be understood more readily by reference to thefollowing detailed description, the examples included therein, and tothe Figures and their following description. The drawings, which are notnecessarily to scale, depict selected preferred embodiments and are notintended to limit the scope of the invention. The detailed descriptionillustrates by way of example, not by way of limitation, the principlesof the invention. The skilled artisan will readily appreciate that thedevices and methods described herein are merely examples and thatvariations can be made without departing from the spirit and scope ofthe invention. It is also to be understood that the terminology usedherein is for the purpose of describing particular embodiments only andis not intended to be limiting.

Referring now in detail to the drawings, in which like referencenumerals indicate like parts or elements throughout the several views,in various embodiments, presented herein is a method for locating acatheter tip by audio detection.

FIG. 1 shows a human body 170 with a catheter 180 inserted at a site 176in the right arm. The catheter 180 has a proximal portion 181 and adistal portion 182. In the present embodiment, the catheter 180 is asingle lumen catheter, but it can have multiple lumens. The proximalportion 181 of the catheter 180 terminates at the luer 184. The distalportion 182 of the catheter 180 terminates in a catheter tip 183. Asshown in FIG. 1, the catheter 180 can be advanced to a target location,such as the superior vena cava 173, or some other site within the humanbody 170, for delivery of fluids such as antibiotics, chemotherapy, painmedicine, nutrition or for withdrawing blood. The user console 10 is adevice, such as a handheld tablet device, which houses the audio signalprocessing unit 100 and a user notification unit 110 for communicatingwith a user. Audio signals emitted from the catheter tip 183 aredetected by one or more audio sensors 101, 102 or 103, transmitted tothe audio signal processing unit 100, and processed for determining thelocation of a catheter tip 183. Once the catheter tip location isdetermined, the audio signal processing unit 100 sends a usernotification signal to the control unit 105, which communicates with theuser notification unit 110 to notify the user. The user notificationunit 110 can utilize a visual display, a sound notification, or somecombination of the two for communicating with the user.

As illustrated in FIG. 2 fluid can be rapidly injected into the lumen ofcatheter 180 and infused through an opening in the catheter tip 183. Asthe fluid 185 ejects through the opening, an audio frequency sound waveis generated. A fluid injection technique called push pause or push stopcan be used to infuse fluid through the catheter 180. The push pausetechnique creates fluid turbulence at the catheter tip 183 generating anaudio frequency sound wave. Increased fluid turbulence facilitates anincrease in the intensity of the generated audio frequency sound wave.For example, a 10 mL syringe can be filled with 10 mL of saline andconnected to the luer 184. Cycles of 2 mL of saline infused over 0.5seconds followed by a 0.5 second pause can be repeated until the 10 mLof saline is fully infused. Other techniques for fluid infusion may beused according to the present invention so that an audio frequencysignal capable of detection is generated at the catheter tip.Additionally, the viscosity of the fluid and the pressure applied to thesyringe by the user can be manipulated to increase the flow rate of thefluid. An increased flow rate may also increase the intensity of thegenerated audio frequency sound wave, facilitating stronger detectionsignals.

Referring back to FIG. 1, the target location for the catheter tip 183is just outside of the heart 172 in the lower ⅓ of the superior venacava 173. A first audio sensor 101 is placed on the anterior side of thebody 170, positioned directly above the lower ⅓ of the superior venacava 173. When a saline bolus is flushed through the opening in thecatheter tip 183, the first audio sensor 101 will detect and measure theemitted audio frequency signal. Utilizing only the first audio sensor101, the audio signal processing unit 100 can indicate whether or notthe catheter tip 183 is the lower ⅓ of the superior vena cava. Thedetermination can be made by implementing audio signal processingtechniques known in the art described in further detail below, includingfiltering the detected audio signal to detect the saline bolus, andcomparing the intensity of the detected audio signal to a baselinesignal or a predetermined threshold level.

In an alternative embodiment, a second audio sensor 102 is placed on theskin above the internal jugular vein 174. If, for example, the cathetertip 183 is unintentionally advanced to the internal jugular vein 174,the second audio sensor 102 will detect the audio signal emitted fromthe saline bolus. Additionally, an absent or weak audio signal will bedetected by the first audio sensor 101, since the audio signal willattenuate over distance. The absent or attenuated audio signal detectedby the first audio sensor 101 is an indication that the catheter tip isin the wrong position. Additionally, if the catheter is fully inserted,the absence of a detected audio signal from both audio sensors couldindicate that the catheter tip has advanced to the subclavian vein, amalfunction occurred in one of the sensors, or that the catheter ismalfunctioning, blocking the saline bolus from infusing through theopening in the catheter tip.

In an alternative embodiment, a third audio sensor 103 is placed on theskin above the subclavian vein 175. Thus, if the catheter tip 183 isunintentionally advanced to the subclavian vein 175, or becomesmispositioned after insertion, the third audio sensor 103 will detectthe audio signal from the saline bolus. Additionally, with respect tothe first and second audio sensors, no audio signal, or a weak audiosignal attenuated by distance may be detected. Further, when thecatheter tip is positioned in a non-target location (e.g. the internaljugular vein or the subclavian vein), the addition of the third sensorprovides the audio signal processing unit 100 with enough data foridentifying specifically which non-target position the catheter tip islocated in.

In an alternative embodiment, first and second audio sensors 101 and 102can be strategically placed for comparing detected audio signals andlocalizing the position of the catheter tip 183. For example, the rightthird intercostal space is commonly used by medical professionals as anexternal reference point for locating the superior vena cava 173.Accordingly, a first audio sensor 101 can be positioned on the skindirectly above the second intercostal space and a second audio sensor102 can be positioned on the skin directly above the fourth intercostalspace. The first and, second audio sensors 101 and 102 should be inalignment with each other and consequently roughly equidistant from thethird intercostal space. As the catheter tip 183 is advanced down thesuperior vena cava 173, the intensity of the audio signal detected fromthe first audio sensor 101 will reach a maximum once the catheter tip183 is directly under the and intercostal space. As the catheter 180advances from the second intercostal space towards the third intercostalspace, the intensity of the audio signal detected by the first audiosensor 101 will decrease as the intensity of the audio signal detectedby the second audio sensor 102 increases. Eventually, the intensity ofthe signals detected by the first and second audio sensors 101 and 102will equalize as the catheter tip 183 is centered directly below thethird intercostal space. According to this alternative embodiment, theaudio signal processing unit 100 can compare the first and seconddetected audio signals for localizing the catheter tip 183.

In an alternative embodiment, a fourth audio sensor can be placed on theskin above a right portion of the subclavian vein. In some instances,the catheter tip 183 returns down the same path from which it wasinserted, for example, in a right portion of the subclavian. This couldhappen if for example the patient moves a lot during insertion and thecatheter tip changes 180 degrees in direction, or the catheter tipbecome mispositioned after initial insertion. Thus, by placing a fourthaudio sensor over a right portion of the subclavian, the audio signalprocessing unit 100 can detect the catheter tip 183 and alert the user.

Referring now to FIG. 3, a flow chart shows an example embodiment of themethod according to the present invention. The patient may be undergoinga procedure for catheter insertion, or maintenance of a previouslyinserted catheter S1. At least one audio sensor 101 is placed above thepatient's skin over the target area of the catheter tip 183 S2. Theaudio sensor 101 is connected or synced to the audio signal processingunit 100 S3. Fluid is injected through the catheter 180 S4 so that anaudio frequency sound wave is generated at the catheter tip 183. Theaudio sensor 101 will detect the audio frequency sound wave generatedfrom the fluid infusion, and the detected audio signal will betransmitted to the audio signal processing unit 100 S5. The audio signalprocessing unit 100 processes the detected audio signal and transmits adetermination regarding tip location to the user notification unit 110S6. The user notification unit 110 displays the tip locationdetermination to the user S7. If the tip location is in the targetlocation S8, the process has ended S10, as the catheter tip 183 isdetermined to be in the target location. If the catheter tip 183 is in anon-target location, or if the tip location cannot be determined S8, theuser adjusts the catheter tip 183 S9 and injects more fluid through thecatheter 180 S4. A new audio frequency sound wave generated from thefluid infusion is detected and transmitted to the audio signalprocessing unit 100 S5. The audio signal processing unit 100 processesthe new signal, sends the determination of tip location to the usernotification unit 110 S6, and communicates that determination to theuser S7. If the ti p is in the target location S8, the process ends S10.Otherwise, the user may repeat steps S4 through S9 multiple times untilthe catheter tip 183 is in the target location. Thus several advantagesof one or more aspects according to this example embodiment are that thecatheter tip of any catheter can be located, regardless of length, sizeor manufacturer. Further, there is no need for a separate styletcomponent, electromagnetic detecting or emitting components, or apatient with a normal sinus rhythm. In addition, the patient is notexposed to harmful radiation, and the operator does not need specialtraining in interpreting x-ray or ultrasound images.

After the audio signal processing unit 100 determines whether or not thedetected audio signal corresponds to the target catheter tip location, anotification signal is sent to a user notification unit 110. Thenotification signal can be sent either directly to the user notificationunit 110, or sent to a control unit 105 that communicates with the usernotification unit 110. The user notification unit 110 can have a visualdisplay for indicating when the catheter tip 183 is in proper position.FIGS. 4A-4D illustrate a user notification display on the user console10 according to an example embodiment. Depending on the determinationmade by the audio signal processing unit 100, the user notification unit110 will display a red light indicating that the catheter tip 183 hasbeen located and is not in the target location, a yellow lightindicating that the catheter tip 183 has not been located, or a greenlight indicating that the catheter tip 183 has been located and is inthe target location. Thus, as shown in FIG. 4A, if the catheter tip 183is located too far away from any one of the sensors, an audio signalemitted from the saline bolus will not be detected, and the yellow lightwill activate. FIG. 4B shows the catheter tip 183 in the target locationof the lower ⅓ of the superior vena cava. The audio signal processingunit 100 will verify that catheter tip in the proper location, thusactivating the green light. FIGS. 4C and 4D show the catheter tip 183after being mispositioned or migrating to the internal jugular vein 174and the subclavian vein 175 respectively, activating the red light. Theuser notification signal can also take other forms, including an audionotification or a message display.

FIGS. 5A-5C show an example embodiment of an audio sensor 101. The audiosensor 101 can be any audio sensor or microphone element capable ofdetecting audio signals emitted from within the human body. In thepresent embodiment, the audio sensor is made of piezoelectricpolyvinylidene fluoride polymer film (PVDF or piezo film). Piezo film isused for various acoustic applications, including contact microphonesfor detecting sounds emitted from within a human body. Piezo film is aflexible, lightweight, highly sensitive thin film capable of being usedas an audio sensor. Piezo film is also immune to moisture, and requiresno external power to function, unlike electrostatic types of audiosensors. FIG. 5A shows an example embodiment of a piezo film audiosensor, with an upper electrode 151, a lower electrode 152, and a pieceof piezo film 153 configured between the upper and lower electrodes. Theelectrodes are silver ink screen printed electrodes, which offer highconductivity, high flexibility and a thin profile. The upper electrode151 and lower electrode 152 overlap at the active piezo film area 154.When the piezo film 153 is stretched, an electrical signal is generatedbetween the upper electrode 151 and lower electrode 152 surfaces at theactive piezo film area 154. The electrical signal is proportional to theamount of elongation of the piezo film 153. The piezo film sensor may becombined with a low-noise electronic preamplifier, and designed tominimize external acoustic noise.

Transmission of detected audio signals to the audio signal processingunit 100 can be accomplished by either hard wired or wirelesstransmission. As shown in FIG. 5B, lead attachments 155 and 156 can beconfigured on the upper electrode 151 and lower electrode 152 using anumber of methods, including for example, eyelets, compression clamping,rivets, crimping, eyelet holes or low temperature solders. The exampleembodiment in FIG. 5B shows first rivet 155 connecting a first wire 157to the upper electrode 151 and a second rivet 156 connecting a secondwire 158 to the lower electrode 152. Lightweight shielded cable ortwisted wire pairs can be used to connect the audio sensor 101 to theaudio signal processing unit 100 while also reducing vulnerability fromunwanted electromagnetic interference.

Now with reference to FIG. 5C, the audio sensor 101 can be designed tovibrate the piezo film through a medium, such as a pad, protectivecoating or protective layer 201. The protective layer 201 may be indirect physical contact with the skin when placed on the body. Theprotective layer 201 can be made of a material compatible for measuringthe audio signal, for example, rubber, a polyester reinforcing member ora thin urethane layer. The protective layer can also be combined with anadhesive for mounting the audio sensor on or near a surface of the skin.Additionally, shielded and low-noise elements can be used to minimizethe amount of ambient noise and interference detected by the audiosensor.

Referring to FIG. 6, detected audio signals are transmitted to the audiosignal processing unit 100 and processed for determining whether or notthe catheter tip 183 is in the target location. In one exampleembodiment, the audio frequency range associated with the sound wavegenerated by a saline bolus is identified. A high-pass filter 166 and alow-pass filter 167 are implemented to remove any frequencies outside ofthat range, such as audio frequencies detected from breathing, bloodflow, body movement or ambient environmental noise. A preamplifier 165can also be connected to the audio sensor to amplify the detected audiosignal. Once frequencies outside of the desired frequency range arefiltered out, an audio signal decision unit 168 determines if theremaining isolated frequencies representing the saline bolus are above apredetermined threshold.

The predetermined threshold can be set based on various factorscorresponding with the catheter tip being located in the targetlocation, including for example a comparison to a baseline audio signal.The baseline audio signal can be established by detecting an audiosignal from the audio sensor before or after the saline bolus isinjected. The detected baseline audio signal can be transmitted to theaudio signal processing unit 100 and stored in memory. The baselineaudio signal can also be manually programed into the memory of the audiosignal processing unit 100. The above described technique audio signalprocessing is one of many known in the art, however, any compatibletechnique can be used according to the present invention.

Referring to FIG. 7, in an alternative embodiment, an electrocardiogramelectrode 161 can be incorporated into the protective layer 201 fortracking electrical activity of the heart. As already known in the art,electrocardiograms can be used for locating catheter tip locations nearthe heart by tracking the change of the P wave as the catheter isadvanced from the upper ⅓ of the superior vena cava down to through thelower ⅓ of the superior vena cava, and into the right atrium 171. Thechange in the P wave on an electrocardiogram monitor correlates to theposition of the catheter tip, typically spiking as the catheter tipenters the right atrium 171. The P wave is reduced as the catheter tipis pulled back from the entrance to the right atrium 171. Thus, thereduced P wave should indicate that the catheter tip is terminated atthe junction of the right atrium and the superior vena cava. In thepresent embodiment, an electrocardiogram electrode 161 is positioned inthe protective layer 201 next to the first audio sensor 101. Theelectrocardiogram electrode 161 transmits detected electrocardiogramsignals to the electrocardiogram signal processing unit 160. The signalis processed and a control unit 105 can verify that the catheter tiplocation determined by the audio signal processing unit 100 isconsistent with the catheter tip location determined by theelectrocardiogram signal processing unit 160. Transmission of theelectrocardiogram signal and detected audio signal can be by a wirelesstransmitter 162. The wireless transmitter 162 can be built into theprotective layer 201 and can communicate with a wireless receiver 163built into the user console 10. The electrocardiogram electrode 161 canalso detect a signal before or after the saline bolus is administeredfor monitoring the heartbeat or establishing an electrocardiogrambaseline.

The user console 10 can be a stationary unit, or a mobile unit such ashandheld device. Further, the audio signal processing unit 100, controlunit 105, user notification unit 110 and electrocardiogram signalprocessing unit 115 can be implemented in hardware, software, or somecombination. For example, in a wireless transmission embodiment, theuser console 10 is a handheld tablet device, and the audio sensorstransmit the measured audio signals to the handheld tablet device usinga wireless protocol such as Bluetooth. The user notification unit 110could incorporate the display of handheld tablet device to communicatewith the user.

Although a saline bolus has been used in example embodiments, thepresent invention is not limited to requiring a saline bolus. Any fluidinfused from a catheter tip will generate an audio signal. Other fluidsmay include heparin based solutions, including for example LactatedRinger's solution and Hartmann's Solution. With respect to infusionrates, although a bolus or rapid infusion of fluid will improve clarityof the detected audio signal, infusion rates may vary depending onvarious factors including the pickup ability of the audio sensors.Further, the audio signal processing unit 100 can be programed tocompensate for changes in fluids and infusion rates.

In an alternative embodiment, a method for locating a catheter tip 183using audio detection uses an audio emitting element positioned at thecatheter tip 183, thus no fluid infusion is required. In an exampleembodiment shown in FIGS. 8A and 8B, a flexible elongated member 190 hasa proximal portion 193 and distal portion 192, terminating in a tip 194at the distal portion 192. Proximate to the tip 194 is an audio emittingelement 191, such as a piezo crystal or a piece of piezo film. Theflexible elongated member 190 can be made of a medical grade flexiblematerial having a diameter smaller than the diameter of the lumen 198 inthe catheter 180. The regions along the flexible elongated member 190can vary in stiffness, depending on the application. The flexibleelongated member 190 may also be made from a guide wire like material.According to the present embodiment, the user console 10 can communicatewith the audio emitting element 191 through communication elements suchas conductive wire or ink that extend through the flexible elongatedmember 190. The communication elements can extend to the proximalportion 193 of the flexible elongated member 190, and can be connectedto an audio signal generating unit in the user console 10. The audiosignal generating unit can set the audio emitting element 191 to emit anaudio beacon signal at a frequency distinct from the audio frequenciesof ambient noise. For example, consideration should be given to bloodflow, breathing, bodily movements and ambient environmental noise.Consideration should also be given to audio sensor position and theimpact that anatomical factors such as body density and bone structurewill have on detection of particular beacon frequencies. According tothis method, the location of any catheter tip can be located, regardlessof length, size or manufacturer.

Alternatively, the sound emitting element can be attached to thecatheter. In the example embodiment shown in FIGS. 8C and 8D, an audioemitting element 195 such as piezo film is attached to or embedded in awall of the catheter distal end portion 182. A first and secondelongated transmission element 196 and 197 extend from the soundemitting element proximally through the catheter wall exiting thecatheter at its proximal end. The exposed communication elements at theluer 184 can be connected to an audio signal generating unit in the userconsole 10. The user console 10 can thus communicate with the audioemitting element 195 to set an audio beacon signal at a distinct audiofrequency. According to these methods for locating the catheter tip, asaline bolus or infusion of fluid from the catheter tip is not required,since the sound emitting element acts as a beacon for the audio sensors.Further, the location of a catheter tip can be determined on initialplacement and subsequent maintenance, and does not require a separatelystocked stylet component.

Some or all of the components mentioned above could be included in akit. The kit may include a user console, audio sensors, wired orwireless signal transmission elements, and instructions for use. The kitmay also include PICC catheters with or without an audio emittingelement, and a stylet with an audio emitting element.

Although it is common to have the catheter tip terminate in a lower ⅓ ofthe superior vena cava, or at the junction of the superior vena cava andthe right atrium, the method according to the present invention can beused for procedures that target any site within the body. Further, anytype of catheter tip can be located, including acute and chronicdialysis catheters, subcutaneous port catheters, and central venouscatheters. In addition, access sites do not need to be in the arm. Forexample, for a patient with amputated arms, the access site may be inthe groin or in the back.

What is claimed is:
 1. A method for locating a catheter tip within ahuman body comprising: positioning a first audio sensor at a first site,infusing fluid through an opening in the catheter tip, the infusion offluid creating a first audio signal, detecting the first audio signalthrough the first audio sensor, transmitting the first audio signalwirelessly from the first audio sensor to an audio signal processingunit, and displaying a notification signal from the audio signalprocessing unit on a user console.
 2. The method of claim 1, wherein thefirst site is located substantially over a lower ⅓ of a superior venacava of the human body.
 3. The method of claim 1, wherein the firstaudio sensor comprises a piezo film element.
 4. The method of claim 1,further comprising: detecting a first baseline audio signal through thefirst audio sensor, transmitting the first baseline audio signalwirelessly from the first audio sensor to the audio signal processingunit, and comparing the first baseline audio signal to the first audiosignal using the audio signal processing unit.
 5. The method of claim 1,further comprising: detecting a first electrocardiogram signal through afirst electrocardiogram electrode, and transmitting the firstelectrocardiogram signal wirelessly from the first electrocardiogramelectrode to an electrocardiogram signal processing unit.
 6. The methodof claim 5, wherein the first audio sensor and the firstelectrocardiogram electrode are operably connected to a first padmember, and wherein the first pad member is positioned at the firstsite.
 7. The method of claim 5, further comprising: detecting a firstbaseline electrocardiogram signal through the first electrocardiogramsensor, transmitting the first baseline electrocardiogram signalwirelessly from the first electrocardiogram sensor to theelectrocardiogram signal processing unit, and comparing the firstbaseline electrocardiogram signal to the first electrocardiogram signalusing the electrocardiogram signal processing unit.
 8. The method ofclaim 1, wherein the fluid is a saline bolus.
 9. The method of claim 1,further comprising: positioning a second audio sensor at a second site,detecting a second audio signal through the second audio sensor, andtransmitting the second audio signal wirelessly from the second audiosensor to the audio signal processing unit.
 10. The method of claim 9,wherein the second site is located substantially over an internaljugular vein.
 11. The method of claim 9, further comprising: detecting asecond baseline audio signal through the second audio sensor,transmitting the second baseline audio signal wirelessly from the secondaudio sensor to the audio signal processing unit, and comparing thesecond baseline audio signal to the second audio signal using the audiosignal processing unit.
 12. The method of claim 9, wherein the firstsite and the second site are located on opposite sides of a thirdintercostal space.
 13. The method of claim 9, further comprising:detecting a second electrocardiogram signal through a secondelectrocardiogram electrode, and transmitting the secondelectrocardiogram signal wirelessly from the second electrocardiogramelectrode to an electrocardiogram signal processing unit.
 14. The methodof claim 13, wherein the second audio sensor and the secondelectrocardiogram electrode are operably connected to a second padmember, and wherein the second pad member is positioned at the secondsite.
 15. The method of claim 13, further comprising: detecting a secondbaseline electrocardiogram signal through the second electrocardiogramsensor, transmitting the second baseline electrocardiogram signalwirelessly from the second electrocardiogram sensor to theelectrocardiogram signal processing unit, and comparing the secondbaseline electrocardiogram signal to the second electrocardiogram signalusing the electrocardiogram signal processing unit.
 16. The method ofclaim 9, further comprising: positioning a third audio sensor at a thirdsite, detecting a third audio signal through the third audio sensor, andtransmitting the third audio signal wirelessly from the third audiosensor to the audio signal processing unit.
 17. The method of claim 16,wherein the third site is located substantially over a subclavian vein.18. The method of claim 16, further comprising: detecting a thirdbaseline audio signal through the third audio sensor, transmitting thethird baseline audio signal wirelessly from the third audio sensor tothe audio signal processing unit, and comparing the third baseline audiosignal to the third audio signal using the audio signal processing unit.